In press working by which workpieces are continuously pressed, a workpiece loading apparatus is used for loading workpieces into a press.
An example of such a workpiece loading apparatus is a sheet loader.
The sheet loader is a type of apparatus peripheral to a press. The sheet loader has a space-saving merit, as it is attached directly to the press.
A known example of such a sheet loader is one which includes a forefront arm and an articulated arm. The forefront arm has at a leading end thereof a holder to and from which a workpiece is attached and detached. The forefront arm is attached to a lower end joint of the articulated arm. The articulated arm has its upper end joint attached to a fixing section adjoining a press. All of the upper end, middle, and lower end joints of the articulated arm have axes of horizontal rotation orthogonal to the direction in which the workpiece is fed. The forefront arm is kept in a horizontal position by rotation about these axes of horizontal rotation (e.g. see PTL 1).
However, the sheet loader described in PLT 1 has a shortcoming of lacking versatility, as it holds a workpiece at one point. That is, the sheet loader can only load workpieces of limited sizes and shapes.
Meanwhile, a loader and unloader apparatus has been under development as the same type of workpiece loading apparatus.
For example, a loader and unloader apparatus with a shift function is known which includes a slider configured to freely shift a workpiece grasping section so that the workpiece grasping section changes its position to grasp a workpiece orthogonally to the direction in which the loader and unloader apparatus travels and a folding mechanism configured to be able of fold only a part of the workpiece that is equivalent to predetermined dimensions (e.g. see PLT 2).
The loader and unloader apparatus is provided with a plurality of suckers and configured to shift the workpiece grasping section, thereby easing to some extent the limitations on the sizes and shapes of workpieces that can be loaded.